Increasing political and environmental pressure is driving the quest for near zero emissive engines and increased efficiency to decrease U.S dependence on foreign oil and reduce greenhouse gas emissions. Fuel cell technology using hydrogen has been widely promoted as an alternative to the fossil fueled internal combustion engine (ICE) due to its perceived superior ability to achieve these goals. Unfortunately, fuel cells have several major hurdles to overcome before widespread use making this possible solution decades away. Meanwhile, the ICE will remain in use until that time.
In the past, the primary advantage of fuel cells over the ICE was potential thermal efficiency. Recent studies by the Department of Energy indicate that the ICE should be capable of producing thermal efficiencies that rival fuel cells. Therefore, a hydrogen fueled ICE promises a much quicker and less expensive option to meet emission and engine efficiency goals.
Using hydrogen as a transportation fuel has several problems. Two important hurdles are the lack of infrastructure to dispense the fuel and storage of hydrogen. Due to the very low density of hydrogen gas, large storage tanks are required to obtain sufficient vehicle range and the storage tanks must withstand relatively high pressures. To avoid these shortcomings, recent work at various research labs has investigated the use of on-board reforming commonly available fuels into higher grade fuels such as syngas and hydrogen. Several test devices have already been successful. While this technology is still being developed, this option appears to be a very promising solution to both the infrastructure and storage problems.
In current Hydrogen engines, backflash, pre-ignition and reduced power are common problems in premixed and port fuel injected engines. One method to minimize or eliminate these shortcomings is to employ direct fuel injection. However, direct injection requires very quick mixing of the hydrogen and air. Often, mixing is incomplete causing misfire, high NOx levels, reduced efficiency, and power loss.
Finally, even with direct injection, pre-ignition remains one of the most difficult challenges to hydrogen use. Compared to gasoline, hydrogen has a much lower ignition energy, wider flammability range and shorter quenching distance making it much more susceptible to engine hot spots and other causes of pre-ignition. New engine architecture is needed not only to address pre-ignition and incomplete mixing, but also other problems associated with conventional hydrogen ICE designs.